Examples of edu.emory.mathcs.backport.java.util.concurrent.locks.Lock

Package edu.emory.mathcs.backport.java.util.concurrent.locks

Examples of edu.emory.mathcs.backport.java.util.concurrent.locks.Lock

edu.emory.mathcs.backport.java.util.concurrent.locks.Lock
ss the resource protected by this lock } finally { l.unlock(); } When locking and unlocking occur in different scopes, care must be taken to ensure that all code that is executed while the lock is held is protected by try-finally or try-catch to ensure that the lock is released when necessary.
Lock implementations provide additional functionality over the use of synchronized methods and statements by providing a non-blocking attempt to acquire a lock ( {@link #tryLock()}), an attempt to acquire the lock that can be interrupted ( {@link #lockInterruptibly}, and an attempt to acquire the lock that can timeout ( {@link #tryLock(long,TimeUnit)}).
A Lock class can also provide behavior and semantics that is quite different from that of the implicit monitor lock, such as guaranteed ordering, non-reentrant usage, or deadlock detection. If an implementation provides such specialized semantics then the implementation must document those semantics.
Note that Lock instances are just normal objects and can themselves be used as the target in a synchronized statement. Acquiring the monitor lock of a Lock instance has no specified relationship with invoking any of the {@link #lock} methods of that instance.It is recommended that to avoid confusion you never use Lock instances in this way, except within their own implementation.
Except where noted, passing a null value for any parameter will result in a {@link NullPointerException} beingthrown.
Memory Synchronization

All Lock implementations must enforce the same memory synchronization semantics as provided by the built-in monitor lock, as described in The Java Language Specification, Third Edition (17.4 Memory Model):
- A successful lock operation has the same memory synchronization effects as a successful Lock action.
- A successful unlock operation has the same memory synchronization effects as a successful Unlock action.
Unsuccessful locking and unlocking operations, and reentrant locking/unlocking operations, do not require any memory synchronization effects.
Implementation Considerations

The three forms of lock acquisition (interruptible, non-interruptible, and timed) may differ in their performance characteristics, ordering guarantees, or other implementation qualities. Further, the ability to interrupt the ongoing acquisition of a lock may not be available in a given Lock class. Consequently, an implementation is not required to define exactly the same guarantees or semantics for all three forms of lock acquisition, nor is it required to support interruption of an ongoing lock acquisition. An implementation is required to clearly document the semantics and guarantees provided by each of the locking methods. It must also obey the interruption semantics as defined in this interface, to the extent that interruption of lock acquisition is supported: which is either totally, or only on method entry.
As interruption generally implies cancellation, and checks for interruption are often infrequent, an implementation can favor responding to an interrupt over normal method return. This is true even if it can be shown that the interrupt occurred after another action may have unblocked the thread. An implementation should document this behavior. @see ReentrantLock @see Condition @see ReadWriteLock @since 1.5 @author Doug Lea

            throw new ManageException("groupid may not be null");
        }


        final GroupResource resource;


        final Lock lock = this.lockManager.getLock(groupid);
        try {
            lock.lockInterruptibly();
        } catch (InterruptedException e) {
            throw new ManageException(e.getMessage(), e);
        }


        try {


            final Element el = this.cache.get(groupid);
            if (el == null) {
                resource = this.newEmptyResource();
                // throws DoesNotExistException if not in db
                this.persistence.loadGroup(groupid, resource);


            } else {
                resource = (GroupResource) el.getObjectValue();
            }


        } finally {
            lock.unlock();
        }


        return resource;
    }

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        if (groupid == null) {
            throw new ManageException("groupid may not be null");
        }


        final Lock lock = this.lockManager.getLock(groupid);
        try {
            lock.lockInterruptibly();
        } catch (InterruptedException e) {
            throw new ManageException(e.getMessage(), e);
        }


        try {
            final GroupResource resource = this.find(groupid);
            resource.remove();
            this.cache.remove(groupid);


        } finally {
            lock.unlock();
        }
    }

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            AuthorizationException {


        String creatorID = caller.getIdentity();
        final String clientToken = req.getClientToken();
        IdempotentReservation res;
        final Lock idemLock = idemManager.getLock(creatorID, clientToken);


        try {
            idemLock.lockInterruptibly();
        } catch (InterruptedException e) {
            throw new CreationException(e.getMessage(), e);
        }


        try {


            res = this.idemManager.getReservation(creatorID, clientToken);
            if (res != null) {


                if (logger.isDebugEnabled()) {
                    logger.debug("Found existing idempotent reservation: " +
                            res.toString());
                }


                // the reservation already exists. check its validity
                return resolveIdempotentReservation(res, req);


            } else {


                final InstanceResource[] resources =
                        this.doCreation(req, caller, bound);


                this.idemManager.addReservation(creatorID, clientToken,
                        Arrays.asList(resources));
                return resources;
            }


        } catch (ManageException e) {
            throw new CreationException(e.getMessage(), e);
        } finally {
            idemLock.unlock();
        }
    }

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        if (logger.isDebugEnabled()) {
            logger.debug("Scheduling file " + file + " for processing");
        }
        getExecutor().execute(new Runnable() {
            public void run() {
                final Lock lock = lockManager.getLock(file);
                if (lock.tryLock()) {
                    boolean unlock = true;
                    try {
                        unlock = processFileAndDelete(file);
                    }
                    finally {
                        if (unlock) {
                            lock.unlock();
                        }
                    }
                }
            }
        });

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                final String correlationId = getCorrelationID(exchange, in);
                if (correlationId == null || correlationId.length() == 0) {
                    throw new IllegalArgumentException("Could not retrieve correlation id for incoming exchange");
                }
                // Load existing aggregation
                Lock lock = getLockManager().getLock(correlationId);
                lock.lock();
                try {
                    Object aggregation = store.load(correlationId);
                    Date timeout = null;
                    // Create a new aggregate
                    if (aggregation == null) {
                        if (isAggregationClosed(correlationId)) {
                            // TODO: should we return an error here ?
                        } else {
                            aggregation = createAggregation(correlationId);
                            timeout = getTimeout(aggregation);
                        }
                    } else if (isRescheduleTimeouts()) {
                        timeout = getTimeout(aggregation);
                    }
                    // If the aggregation is not closed
                    if (aggregation != null) {
                        if (addMessage(aggregation, in, exchange)) {
                            sendAggregate(correlationId, aggregation, false);
                        } else {
                            store.store(correlationId, aggregation);
                            if (timeout != null) {
                                if (log.isDebugEnabled()) {
                                    log.debug("Scheduling timeout at " + timeout + " for aggregate " + correlationId);
                                }
                                getTimerManager().schedule(new TimerListener() {
                                    public void timerExpired(Timer timer) {
                                        AbstractAggregator.this.onTimeout(correlationId);
                                    }
                                }, timeout);
                            }
                        }
                    }
                    done(exchange);
                } finally {
                    lock.unlock();
                }
            }
        // Handle an ACTIVE exchange as a CONSUMER
        } else if (exchange.getStatus() == ExchangeStatus.ACTIVE) {
            done(exchange);

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    protected void onTimeout(String correlationId) {
        if (log.isDebugEnabled()) {
            log.debug("Timeout expired for aggregate " + correlationId);
        }
        Lock lock = getLockManager().getLock(correlationId);
        lock.lock();
        try {
            Object aggregation = store.load(correlationId);
            if (aggregation != null) {
                sendAggregate(correlationId, aggregation, true);
            } else if (!isAggregationClosed(correlationId)) {
                throw new IllegalStateException("Aggregation is not closed, but can not be retrieved from the store");
            } else {
                if (log.isDebugEnabled()) {
                    log.debug("Aggregate " + correlationId + " is closed");
                }
            }
        } catch (Exception e) {
            log.info("Caught exception while processing timeout aggregation", e);
        } finally {
            lock.unlock();
        }
    }

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public class SimpleLockManager implements LockManager {


    private ConcurrentMap locks = new ConcurrentHashMap();
    
    public Lock getLock(String id) {
        Lock lock = (Lock) locks.get(id);
        if (lock == null) {
            lock = new ReentrantLock();
            Lock oldLock = (Lock) locks.putIfAbsent(id, lock);
            if (oldLock != null) {
                lock = oldLock;
            }
        }
        return lock;

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            logger.debug("Scheduling file " + aFile + " for processing");
        }
        getExecutor().execute(new Runnable() {
            public void run() {
                String uri = file.toURI().relativize(aFile.toURI()).toString();
                Lock lock = lockManager.getLock(uri);
                if (lock.tryLock()) {
                    boolean unlock = true;
                    try {
                        unlock = processFileAndDelete(aFile);
                    }
                    finally {
                        if (unlock) {
                            lock.unlock();
                        }
                    }
                } else {
                    if (logger.isDebugEnabled()) {
                        logger.debug("Unable to acquire lock on " + aFile);

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        }
    }


    public ConstraintInfo[] get_constraints(int[] ids) throws ConstraintNotFound
    {
        final Lock _lock = constraintsLock_.readLock();


        _lock.lock();
        try
        {
            final ConstraintInfo[] _constraintInfo = new ConstraintInfo[ids.length];


            for (int _x = 0; _x < ids.length; ++_x)
            {
                Integer _key = new Integer(ids[_x]);


                if (constraints_.containsKey(_key))
                {
                    _constraintInfo[_x] = ((ConstraintEntry) constraints_.get(_key))
                            .getConstraintInfo();
                }
                else
                {
                    throw new ConstraintNotFound(ids[_x]);
                }
            }


            return _constraintInfo;
        } finally
        {
            _lock.unlock();
        }
    }

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        }
    }


    public ConstraintInfo[] get_constraints(int[] ids) throws ConstraintNotFound
    {
        final Lock _lock = constraintsLock_.readLock();


        _lock.lock();
        try
        {
            final ConstraintInfo[] _constraintInfo = new ConstraintInfo[ids.length];


            for (int _x = 0; _x < ids.length; ++_x)
            {
                Integer _key = new Integer(ids[_x]);


                if (constraints_.containsKey(_key))
                {
                    _constraintInfo[_x] = ((ConstraintEntry) constraints_.get(_key))
                            .getConstraintInfo();
                }
                else
                {
                    throw new ConstraintNotFound(ids[_x]);
                }
            }


            return _constraintInfo;
        } finally
        {
            _lock.unlock();
        }
    }

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Examples of edu.emory.mathcs.backport.java.util.concurrent.locks.Lock

Memory Synchronization

Implementation Considerations

Related Classes of edu.emory.mathcs.backport.java.util.concurrent.locks.Lock